I understand where you're coming from Manx... and if I felt that the backstories where completely useless like you do, then I'd have ditched the show too.
The show definately re-negged on a lot of things... introducing all of these weird ideas about what's going on on the island, but never really delivering on any of it. Then they go ahead with all these back stories... but are these stories just filler used to avoid the questions they don't want to answer, or are the backstories really what the show is about? I guess you have to decide for yourself.
Personally, I love the back stories. They're well done and help to really flesh out who these people are. I usually like things to be more character-based than plot-based anyway... so I guess that's why I've been so forgiving up to now. I'd like to think I'd still like the show even if it didn't have all this weird stuff happening on the island. But that weird stuff does provide some excitement and gets people hooked. Meh, so be it.